Bifunctional air or oxygen depolarization cells are generally well known in the art. Electro-chemical cells of this type include a gas diffusion electrode capable of generating electricity by electro-chemically combining an oxidizable reactant with a reducible reactant. Generally, these electro-chemical cells are comprised of spaced apart electrodes ionically connected by an electrolyte.
Illustrative of these types of cells and electrodes is Buzzelli, U.S. Pat. No. 3,977,901, herein incorporated by reference. In that patent, particular types of low surface area carbon black materials were used to help solve problems of electrolyte permeability. Other components used in the electrodes of that patent included 0.5 to 4 parts, per 1 part of carbon, of an oxygen evolution material, such as WC, and effective amounts of both a bonding/nonwetting agent and a catalyst for oxygen reduction and decomposition of perhydroxides, such as silver.
Such electrodes were found to have third cycle charging potentials of about 550 mV. to 610 mV. vs. a Hg/HgO reference electrode. Values of about 550 mV. to 585 mV. were achieved by using major amounts of oxygen evolution material, such as WC, adding substantially to the cost and weight of the electrode. It is desirable to lower this charging voltage, to conserve energy, and to reduce the amount of silver catalyst that dissolves in the electrolyte at that voltage. It is also desirable to reduce the cost and weight of the above-described types of electrodes, while maintaining a proper balance of electrolyte permeability.
In another art area, relating to graphite anodes used in the electrolysis of aqueous alkali metal halide electrolyte, Curry et al., in U.S. Pat. No. 3,580,824, taught vacuum impregnating a graphite anode with ferric or ferrous chloride, nitrate, acetate or formate, and then calcining the impregnated graphite for up to 4 hours at 800.degree. C. to 2,000.degree. C. in an inert atmosphere, to produce varying amounts of alpha-iron and alpha-Fe.sub.2 O.sub.3, in-situ in the graphite pores. The iron is used partly as a substitute for an oil impregnant, to reduce the consumption of the anode during cell operation, the iron apparently preventing wetting of the interior of the anode by the liquid electrolyte. Such a process would make the electrode substantially electrolyte impermeable.